Ampere-level CO electroreduction with single-pass conversion exceeding 85% in acid over silver penetration electrodes.

Synthesis of valuable chemicals from CO electroreduction in acidic media is highly desirable to overcome carbonation. However, suppressing the hydrogen evolution reaction in such proton-rich environments remains a considerable challenge. The current study demonstrates the use of a hollow fiber silver penetration electrode with hierarchical micro/nanostructures to enable CO reduction to CO in strong acids via balanced coordination of CO and K/H supplies. Correspondingly, a CO faradaic efficiency of 95% is achieved at a partial current density as high as 4.3 A/cm in a pH = 1 solution of HSO and KCl, sustaining 200 h of continuous electrolysis at a current density of 2 A/cm with over 85% single-pass conversion of CO. The experimental results and density functional theory calculations suggest that the controllable CO feeding induced by the hollow fiber penetration configuration primarily coordinate the CO/H balance on Ag active sites in strong acids, favoring CO activation and key intermediate *COOH formation, resulting in enhanced CO formation.